In this chapter, we are going to look at Spanish and English
words that contain some version of a root that means ‘foot’. The English word foot and the Spanish word pie do not look or sound alike at all,
but they are patrimonial cognates. This means that they are patrimonial words in
their respective language, not loanwords, and that they go back to the same word
in the language that is the ancestor to both languages, namely in Proto-Indo-European.
We do not have any records of this language that was spoken over 5,000 years
ago, but linguists have established its existence by comparing daughter
languages derived from it. And the word for ‘foot’ was transmitted orally for thousands
of years all the way to the present time in each of these languages. The connection
is not so surprising once we realize that linguists have established that Proto-Indo-European
p and d mutated into Germanic f
and t, respectively (see Part I,
Chapter 3,
§3.6.5).

The English word foot
/ˈfʊt/, plural feet /ˈfit/, is a native,
Germanic word, the root of which was fōt
/ˈfoːt/ in Proto-Germanic, the language that English, German, and other European
languages come from. The Spanish word pie
/ˈpi̯e/, plural pies /ˈpi̯es/ (it was
piedes until the 13th century),
is a native word too, one which goes back to the Latin root pĕd- /ˈped/. This word had
an irregular nominative case form, namely pēs,
but its accusative case form was pĕdem,
and that is the form that Sp. pie derives from.

Both of these words go back to the same Proto-Indo-European root
*pōd- ‘foot’. Proto-Germanic,
the ancestor of English, changed the Proto-Indo-European consonants p and d to f and t, respectively), and Latin, the ancestor
of Spanish, changed the vowel o to e. Other than that, foot and pie are (what linguists call) modern reflexes of the same original word in two different daughter
languages.

Of course, if you didn’t know about those sound changes,
you would have never guessed that these words are cognates, both in the sense
of the word cognate used in this book (words derived from the same original
source word) and in the sense of the word cognate used in linguistics (words
derived from the same original source word that are not loanwords). Obviously,
however, these two words are not cognates in the sense of the word used in
language study (words that look alike and have the same meaning).

Proto-Indo-European

pod-

Germanic

fōt

Latin

ped-

English

foot (pl. feet)

Spanish

pie

How we get from the Proto-Indo-European word to the English
and the Spanish ones is easy to explain by regular sound-change rules that have
been well known for over a century. So, as we said, in the Germanic branch of
daughter languages, Proto-Indo-European p
changed to f and d changed to t, both changes
predicted by Grimm’s Law (see, Part I,
§3.6.5).

The relationship between the singular and the plural
of the English word (foot-feet) is also explained by a regular phenomenon
known as i-mutation, umlaut, or metaphony,
by which a back vowel, in this case the /ʊ/ in the singular word foot, becomes fronted to /i/ in
anticipation of a similar sound in the suffix (cf. Part I, Chapter 7).
This is a sound mutation that took place in many Germanic languages around 1,500
years ago.

The phenomenon of i-mutation
or i-umlaut in Old English originally
resulted in the change of vowels, such as the one we see here, when the sound in
the following syllable was /i/ or /j/, as in the plural suffix ‑iz and the noun suffix ‑ith (that derived nouns from adjectives,
e.g. filth < foul).[i]
Although some of the vowel changes that took place have been reversed over the centuries
by other regularizing processes, we still find reflexes of this change in singular-plural
pairs such as foot-feet /ˈfʊt ˈfit/, mouse-mice /ˈmaʊ̯s ˈmaɪ̯s/ (pronounced /ˈmus ˈmis/ until about 500 years ago), and man-men
/ˈmæn ˈmɛn/.

As we said earlier, Spanish pie is derived from the accusative form of Latin pēs, namely pĕdem. In this word the final -m was lost first, very early on, giving us
pede. Then the stressed ĕ became the diphthong ie [i̯e], cf. piede. This
is what happened to the short vowel ĕ
in Latin as it morphed into Spanish if it was stressed. Then, the d was lost between vowels as it
typically did, giving us *piee. Finally
the resulting ee were simplified to a
single e (pie), which is also an expected development. The changes are summarized
thus:

Latin pĕdem > pede > piede > piee > Mod. Spanish pie

The Latin word pēs evolved differently in other Romance languages:

Mod. French pied
(Old French pié): the d, which is not
pronounced, was added in recent times to the spelling of the word to make it
look more like its Latin source word

Portuguese pé
(Old Port. pee): in Portugues, Latin
short ĕ did not become a diphthong

Catalan peu
(a variant of Old Provençal pe)

Italian piede:
here the ĕ
became a diphthong, but the d
was not lost

English foot
and Spanish pie are not the only patrimonial
cognates that refer to body parts, though there aren’t very many of them. We find
a few other such cognates, having to do with body parts. Sometimes, such pairs are
not full cognates (sharing the root and all affixes), but they at least share
the word’s root in the original source word. All of those pairs of cognates
look very different from each other at first sight in the modern languages, since
they split from the original source word thousands of years ago and the sounds
in these words have mutated independently of each other (though not their meaning,
in this case). The main such cognate words are the following: